This invention relates to apparatus for transmission of infrared radiation, particularly infrared laser radiation, and in particular to flexible structures for transmission of infrared radiation at low loss.
At the present time, optical fibers are widely used for transmission of radiation in the visible portion of the spectrum. The fibers are highly flexible and permit moving and steering of the light. The fiber optic systems are particularly valuable in endoscopes and similar instruments which provide for inspection of the interior of body organs such as the stomach.
Infrared radiation, typically from a laser source, is used today in a variety of applications including welding, cutting and surgery. There is a need for a flexible system for delivery of infrared radiation to a target; however, fibers transparent in the infrared region have not been developed. Rather complex and delicate articulated arm optical systems are being used for guiding infrared beams.
Accordingly, it is an object of the present invention to provide a new and improved apparatus for transmitting and steering infrared radiation. A particular object is to provide such an apparatus which is small and flexible and which can handle a high energy beam with low loss.
Cylindrical hollow dielectric guides have been used for transmission of radiation from carbon dioxide lasers which operate in the infrared region, typically at 10.6 micrometers. However these wave guides are not flexible and cannot be used in a flexible application because of the large bending losses.
Hollow rectangular metal wave guides are used for the transmission of energy in the microwave region, utilizing single mode structures having a width to heighth ratio in the order of 2 to 1. However the theory of operation of the microwave wave guide indicates that the wave guides will not be satisfactory for transmission of infrared radiation.
An article entitled Low-Loss Parallel-Plate Wave Guide at 10.6 .mu.m by Nishihara et al appearing in Applied Physics Letters, Volume 25, Number 7, Oct. 1, 1974 at pages 391-393 discloses the use of a planar metallic wave guide in the infrared region, showing an open sided guide with curved surfaces, with the width to heighth ratio being infinite. This infinite width structure suffers from leakage of energy at the open sides and is not readily bent or twisted.
It is an object of the present invention to provide a new and improved hollow rectangular wave guide suitable for transmission of energy in the infrared portion of the spectrum, with the wave guide being readily bent and twisted without introducing appreciable loss in the transmission.